Power reverse gear



March 1937. E. M. sHANNoN ET AL I 2,072,410

POWER REVERSE GEAR Filed Sept. 29 i935 2 Sheets-Sheet 1 INVENTORS Ellwood M. Shannon J Mznamm March 2, 1937 E. M. SHANNON ET AL Filed Sept. '29, 195:

2 Sheets-Sheet 2 Fig.2

I Patented Mar. 2, 1937 i PATENT OFFICE POWER REVERSE GEAR Ellwood M. Shannon, Bala, and James F. McMenamin, Philadelphia, Pa.

Application September 29, 1933, Serial No. 691,460

" Claims.

This invention relates generally to power reverse mechanism for locomotives and more particularly to an improved valve mechanism for the reverse motor.

"5 Power reverse motors of the piston cylinder type are actuated by fluid pressure, such as air or steam, usually simultaneously admitted to both ends of the cylinder to hold the piston in fixed position after any adjustment thereof while an exhaust passage is adapted to be connected to either end of the cylinder to effect movement of the piston. While theoretically it is possible to hold the piston in a given position after adjustment, yet in actual practice it is found that the piston will gradually creep in one direction or the other, thus undesirably changing the cut-off. As a result the engineer must carefully watch the operation of the locomotive to correct any creeping action of the power reverse motor. Hence this creeping is a very annoying problem not only to the engineer but also to manufacturers of power reverse motors.

While various attempts have been made to prevent creeping, such as the provision of mechanical stops engageable with the piston rod, wedges operated against the rod and various restoring mechanisms, yet such attempts have not presented a complete solution to the problem either from an operating or manufacturing standpoint. Such devices are not only too expensive either in manufacture or maintenance, but are not as effective in operation as is desired because of not eliminating the source of difficulty.

The most desirable solution to any problem is to eliminate the source of the trouble rather than in allowing the source to remain and then trying to control the adverse effects thereof, providing of course that it may be done economically and effectively. From this aspect of the situation we have found that one source of difiiculty may be most effectively and economically eliminated by having the valve mechanism so arranged that when it isin neutral position it will close off the exhaust port as well as the cylinder ports or passages leading to the cylinder ends, although it will of course be understood that the closure of the cylinder ports refers broadly to either the type of valve where the supply of fluid pressure is in constant communication simultaneously with 5.0

55 to provide an improved valve for accomplishing both ends of the cylinder through a small negative r lap when the valve is in neutral position or it may the foregoing results and in one specific aspect of the invention this is done by simultaneously substantially closing the cylinder ports and exhaust port with a disc-like or flat valve having a central hollow portion through which one or the other 5 of the cylinder ports communicate with the exhaust port, said hollow portion being provided with a, bridge constituting a valve for closing the exhaust passage when the valve is in neutral position.

A further object is to provide improved means for maintaining the valve in neutral position which in one specific aspect of the invention is accomplished by having a latch mechanism directly cooperating with the valve for holding the 16 same in neutral position independently of the yalve actuating means. Another object is to provide an improved combination whereby when the Valve is near its neutral position it will be slightly moved to its precise neutral position independent- 2 1y of the valve actuating means.

With the foregoing improved valve structure and means for moving the same to and holding it in its neutral position, we have reduced or eliminated certain causes of creeping rather than at- 25 tempted to prevent creeping without eliminating the causes thereof. Also it will be seen that our improved results and mode of operation are accomplished in a relatively simple and highly effective manner.

Other objects and advantages will be more apparent to those skilled in the art from the following description of the accompanying drawings in which:

Fig. 1 is a vertical section through a valve mech- 35 anism and a part of the actuating means therefor including a portion of a floating lever;

Fig. 2 is a horizontal section taken on the line 2-2 of Fig. 1, showing the valve in neutral position;

Fig. 3 is a section similar to Fig. 2 but showing the valve moved to the left of its neutral position thereby to exhaust one end of the motor and admit fluid pressure to the other end thereof;

Fig. 4 is a vertical-section taken substantially on the line 4-4 of Figs. 1 and 2.

In the particular embodiment of the invention whichv is disclosed herein merely for the purpose of illustrating one specific form among possible others that the invention might take, We have diagrammatically shown a power reverse motor cylinder at l which as is well known carries a valve mechanism generally indicated at 2 for distributing actuating fiuid to or exhausting fluid from the opposite ends of the cylr inder I. The valve mechanism includes a body 3 secured to the top of the cylinder by bolts or other suitable means. Removably secured to one end of housing 3 is a circular valve seat block 4 fitting within a stationary valve housing 5 which is held in fixed relation to valve body 3 by bolts passing through lugs 6, valve housing 5 being preferably seated within a slight recess in the end of body 3. Seat block 4 has a central circular opening receiving an enlarged cylindrical portion of a head 6 formed on a valve actuating shaft 7, this shaft being suitably journalled in body 3. The head 6 has its innermost end preferably flatted and tapered at 8 to fit within a preferably slightly enlarged rectangular recess 9 of a valve l0 although this recess under certain conditions may have various degrees of enlargement, but in any event the enlargement forms a lost motion connection between the distributing valve and its operating mechanism. This valve as shown is generally of the disc or flat type journalled upon the inner end of said cylindrical portion of head 6. A spring I! holds the valve H) in position against the valve seat block 4 while an inner spring l2 seats against valve H] to yieldably restrict axial movement of shaft 1.

As shown in Fig. 2 the body 3 is provided with cylinder ports I5 and [6 leading respectively to the opposite ends of the cylinder of power reverse motor I while an exhaust passage or port l1 discharges to the atmosphere. The valve seat block 4 has ports I5, l6, and I1 registering with ports l5, l6, and H. The detailed arrangement of the passages l5, I6, and 11 within the body 3 is not an essential part of our present invention, and hence the foregoing disclosure will suffice. The ports as shown in Fig. 4 are preferably arranged in an arc and are surrounded by a valve seat surface 20.

Valve H] as, is usual in this general type of valve has a short arcuate hollow portion 2| provided at its ends with valve portions 22 and 23. When the valve is in neutral position, these valve portions 22 and 23 have a slight positive lap with the inner edges of ports I5 and I6 and have a small amount of negative lap with the outer edges of said ports, although this could be a positive lap depending upon the particular mode of operation desired.

In our improved arrangement we have further provided a valve portion or bridge 24 having a positive lap on each edge of exhaust port ll. Hence with the valve in neutral position, the exhaust port is fully positively covered simultaneously with the covering of the inside or discharge edges of the cylinder ports l5 and I6. Hence with the four lapped edges it is possible to reduce leakage to a minimum and thereby effectively decrease the possibility of creeping as well as to eliminate constant operation of the follow-up mechanism usually employed with the valves for power reverse motors.

The follow-up mechanism is only partially indicated in Fig. l as including a floating lever 25 pivotally connected as its upper end to a pin 26 which is carried in an arm. 21. This arm is secured to actuating shaft 1 so as to rotate the same with valve [0 as through the flatted head 8. A reach rod (not shown) is suitably connected usually at 25a to the floating lever while usual restoring mechanism is connected to the lower end of the floating lever and the piston rod of the reverse motor.

To insure return of the valve precisely to its neutral position and to maintain the same in neutral, we have provided improved means including a latch pin 28 normally pressed inwardly by a spring 29 and prevented from rotating by a removable threaded stud 30 guided in a slot. The latch pin is disposed in a bore formed within a suitable boss 31 on the valve housing 5 thereby insuring complete enclosure of the latch pin and freedom from dirt. At the same time latch pin 28 is permitted to have direct engagement with valve Ill as through a wear plate 32 removably secured as by bolts or the like to the valve preferably adjacent the ports l5, l6, and [1. This arrangement permits spring 29 to hold the valve more firmly against its seat by applying the pressure in alignment therewith. The wear plate is provided with a small inclined radial notch 34 for receiving the tapered end of pin 28, although broadly the term notch refers to any detent, recess or the like whereby the valve may be held in neutral position or, if desired, the detent and pin may be provided as shown with relatively inclined surfaces to obtain a component rotating force.

Notch 3d and pin 28 are so located that when in engagement the valve is held in its neutral position. The slightly enlarged rectangular recess 9 in valve l3 permits a small amount of movement of the valve relative to fiatted head 8 when near neutral position. Hence if the operating linkages should be slightly worn or out of adjustment so as not to move the valve precisely to its neutral position, then the inclined surface of pin 28, when once in engagement with any portion of the inclined surface of notch 34, will force the valve sideways until the pin is fully seated within said notch.

As is usual in this general type of valve mechanism, fluid pressure is initially supplied to the inside of valve housing 5 as through an air passage 38 or if steam is used then through a passage 39, one of these passages being closed off when the other is used.

From the foregoing it is seen that We have provided a relatively simple and yet very effective means for eliminating or appreciably reducing the source of creeping in power reverse gears thereby avoiding the necessity of mechanical piston stops or other usual locking devices. Also in our improved arrangement when the valve is in or near neutral position, it is independent of its actuating means and yet is controlled by auxiliary means, such as the latch pin, to move the valve to and releasably hold the same in neutral position. In this position the two edges of the exhaust port are positively lapped. This double lap together with the single positive lap of each of the inside edges of the cylinder ports gives a double seal between each cylinder port and exhaust port in a simple and inexpensive manner. These elements cooperate to produce a most eflicient power reverse motor.

It will of course be understood that various changes in details of construction and arrangement of parts may be made by those skilled in the art without departing from the spirit of the invention as set forth in the appended claims.

We claim:

1. A valve mechanism for a power reverse motor comprising, in combination, a valve body having a plurality of cylinder ports and an exhaust port, and an oscillatable fiat valve element having a double lap closure for said exhaust port and a single lap closure of each of said cylinder ports.

2. A valve mechanism for a power reverse motor comprising, in combination, a valve body having a pair of cylinder ports and an intermediate exhaust port, said ports being surrounded by a flat valve seat surface, and a valve element having provision for overlying both of said cylinder ports when the valve is in neutral position and also having a hollow portion for allowing communication between either one of said cylinder ports and said exhaust port when the valve is moved from its neutral position, andv a bridge in said hollow portion adapted to close said exhaust port when the valve is in neutral position and to uncover the same when the valve is moved in either direction therefrom.

3. The combination set forth in claim 2 further characterized in that said bridge positively laps each edge of said exhaust port.

4. The combination set forth in claim 2 further characterized in that the valve closure for the cylinder ports has a positive lap for one edge of the cylinder ports.

5. The combination set forth in claim 2 further characterized in that the bridge positively laps each edge of the exhaust port and the valve positively laps the edges of the cylinder port-s adjacent to the exhaust port thereby to provide multiple positive laps through which fluid would have to pass in case of leakage from the cylinder port to the exhaust ports.

6. The combination set forth in claim 2 further characterized in that a valve housing encloses the valve element to provide a fluid pressure chamber, whereby fluid pressure supplied to said chamber is admitted to said cylinder ports past the outer edges of said valve element and communication between said cylinder and exhaust ports is effected through the hollow portion of said valve past said bridge.

'7. A valve mechanism for a power reverse motor comprising, in combination, an oscillatable distributing valve having a fiat seat engaging surface, and means acting directly on said valve for returning it to neutral position only when the valve is near its neutral position. I

8. A valve mechanism for a power reverse motor comprising, in combination, an oscillatable distributing valve having a flat seat engaging surface, a notch in one side of said valve, and means engageable with said notch substantially only when said valve is in neutral position and is disengaged from said notch when said valve is substantially displaced from neutral.

9. A valve mechanism for a power reverse motor comprising, in combination, an oscillatable distributing valve having a fiat seat engaging surface, a cover therefor, and means for holding said valve when in neutral position including a member yieldable axially of said axis of oscillation and carried by said cover and uniformly slidably engaging said valve when it is away from its neutral position.

10. A valve mechanism for a power reverse motor comprising, in combination, an oscillatable distributing valve, operating mechanism therefor having a lost motion connection therewith, and means directly associated with said valve and including relatively inclined surfaces yieldably pressed together when said valve is in substantially its neutral position whereby said lost motion connection allows the coaction between said surfaces to effect movement of the valve to its neutral position.

ELLWOOD M. SHANNON. JAMES F. MoMENAMIN. 

